Forward Bends are back stretching Āsana in terms of Bhāvana.
Thus in PaścimatānaĀsana one of the foci is on avoiding pushing
from the lower back as you bend forward.
Thus move forward from the abdominal area by drawing it back,
to encourage the lower back to respond by lengthening.
If we push from the lower back in forward bends,
such as Paścimatānāsana,it can tighten this area,
thus inhibiting the focus on the quality of the ApānaLakṣaṇa,
as well as transferring stress to the sacrum, hips and hamstrings.